Speech fluency and hand performance on a sequential tapping task in left- and right-handed stutterers and nonstutterers

The purpose of this study was to examine hemispheric functioning in right- and left-handed stutterers and nonstutterers using tasks that require concurrent speech and unimanual sequential tapping activity. Twenty adult stutterers (15 right-handers and 5 left-handers) and 20 adult nonstutterers (15 right-handers and 5 left-handers) performed four experimental tasks: tapping, tapping-spontaneous speech, tapping-reading, and tapping-singing. Subjects performed each task for 120 sec (8 trials of 15 sec per trial), alternating tapping hands after each trial.Results indicated that subjects' speech and manual performance were hindered by the concurrent motor activities and that stutterers demonstrated more interference than the nonstutterers. In addition, the tapping-spontaneous speech task resulted in the greatest interfering condition. Results suggest that both intrahemispheric competition and interhemispheric integration processes are involved in the regulation of speech and motor activities. Moreover, the possibility exists that a key difference between stutterers and nonstutterers may be linked to the degree to which these activities are synchronized.